March 25, 2005 | By: Laura Skillman
PRINCETON, Ky.

Last year’s cool, wet conditions during much of the growing season resulted in high levels of Northern leaf blight in some Kentucky corn fields. With the high incidence in 2004, more of the fungus that causes the disease has likely overwintered in fields across the state.

Today, the fungus is overwintering in corn residue, and the combination of the high levels of disease last year and the mild winter has allowed the fungus to sustain itself at pretty high levels, said Paul Vincelli, a plant pathologist with the University of Kentucky College of Agriculture. Under the right environmental conditions, the disease is poised to cause substantial problems.

“From our eyes, last year was a very impressive outbreak,” Vincelli said. “It’s kind of scary the amount of damage it could cause.”

Severe yield loss can occur when leaves become blighted during early grain fill. The disease is more severe in fields with corn following corn under reduced tillage. When you have severe leaf blight you may have lodging and as the corn tries to fill grain, it is going to pull food from the stalk and weaken the stalk.

“We have levels of spores out there now that are much higher than we are used to having,” he said. “If we have a hot, dry year we probably won’t see any real problems. Even a year with weather more typical of our average conditions will probably not lead to serious problems. However, if we get into another year of cool, wet weather – unlikely but not outside the realm of possibility – we could be facing some very, very serious problems. My hope is that we don’t see Northern leaf blight like this, but producers need to be aware we could have a situation if we have sustained cool, wet weather.”

There are hybrids that have a high degree of resistance to the disease, and there are hybrids with low to moderate resistance. Where the disease is known to occur, Vincelli recommends using resistant hybrids, especially when grown without rotation under conservation tillage.

Producers should consider the level of susceptibility for all hybrids to be planted in 2005, but especially in or near fields under conservation tillage where Northern leaf blight occurred this past season, he said. 

“The law of averages suggests that next season is not likely to be as cool, cloudy, and wet as this past season, in which case many producers would ‘dodge a bullet’,” Vincelli said. “However, with the high inoculum levels that are present in certain areas, especially in western Kentucky, a repeat of the same kind of weather could result in destructive epidemics on susceptible varieties in some localities.”

There are some fungicides that are effective on the fungus but Vincelli said he sees no reason why most fields would need to be treated with fungicide. In most fields, a combination of rotation and selection of a hybrid with moderate to high resistance should help keep Northern leaf blight from causing damaging yield losses.

In Christian County, there were some instances of blight in 2004, said Jay Stone, county Extension agent for agriculture and natural resources. Corn stubble is not has high a concern in his county because most of the fields are rotated into wheat following corn, helping reduce the residue.

Stone said he expects farmers who suffered damage due to Northern leaf blight to be more aware of hybrid selection but he’s not sure they will switch from less resistant varieties that have yielded consistently for them in the past especially since blight has not been much of an issue except in 2004.

For more information on Northern leaf blight or other corn diseases, contact a county Extension office.
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Writer: Laura Skillman, 270-365-7541 ext. 278
Sources: Paul Vincelli, 859-257-7445 ext. 80722; Jay Stone, 270-886-6328
 


Contact: 

Writer: Laura Skillman 270-365-7541 ext. 278

Contacts: Paul Vincelli 859-257-7445, ext. 80722
Jay Stone 270-886-6328